A monitoring camera is installed at a monitoring place to photograph and record a moving image of a monitoring target. In recording of a moving image of a monitoring target, a moving image to be recorded includes a frame having a high degree of importance, a frame having a low degree of importance, and a frame having an intermediate degree of importance together. For example, in the monitoring camera, a frame in which a person's face or a vehicle's license plate is photographed is an important frame, but a frame in which only a background is shown and a frame having little difference with a previous frame are a frame having a low degree of importance. Further, depending on the installation position of the monitoring camera, many frames having a high degree of importance may be photographed, or many frames having a low degree of importance may be photographed.
If it is possible to photograph and record an important frame at a high image quality and to photograph and record a frame having a low degree of importance at a low image quality when photographing and recording a moving image, it is possible to effectively use a limited memory capacity without damaging the purpose of monitoring, and it is possible to reduce a load of a network without damaging the purpose of monitoring even when a moving image is transmitted. Here, as a factor influencing an image quality of a moving image, there are a frame rate of a moving image and a compression rate in an encoding unit.
In the past, a method of adjusting an image quality according to a degree of importance of a moving image has been proposed (for example, see JP 2009-55341 A). According to the method of the related art, when a plurality of monitoring cameras are installed, it is possible to set an image quality of each monitoring camera according to a degree of importance by setting a recording period of time and a degree of importance (which is represented by an integer value of 1 to 10) of each monitoring camera in advance. Further, even when the number of monitoring cameras has been increased or even when the capacity of a recording device has been changed, an image quality can be adjusted only by resetting a recording period of time and a degree of importance.
Further, according to the method of the related art, by setting a degree of importance of a certain periodic time zone in advance, it is possible to dynamically adjust an image quality, for example, it is possible to change a degree of importance according to a time zone.
However, the method of the related art has the following problems. One is a problem caused as it depends on a hunch to represent a degree of importance by a numerical value in advance, and another is a problem caused as a temporal change in a degree of importance is fixedly set in advance. The problems will be described below.
FIG. 14 is a graph illustrating an example of a change in a degree of importance when a monitoring camera is installed in a retail store. A solid line represents a change in an actual degree of importance. For example, the actual degree of importance is calculated based on the number of visitors. The actual degree of importance increases after 8:00 which is an opening time of the retail store, and decreases before 22:00 which is a closing time. In the method of the related art, a degree of importance is set based on the actual degree of importance such that a degree of importance is high in a time zone of 8:00 to 22:00 which are opening hours, and a degree of importance is low in the remaining time zones, as indicated by a dotted line.
FIG. 15 is a graph illustrating an example of a change in a degree of importance when a monitoring camera is installed in a retail store. In the graph of FIG. 15, actual degrees of importance of different seasons are added to the graph of FIG. 14. In FIG. 15, an alternate long and short dash line represents a change in an actual degree of importance in winter, and a solid line represents a change in an actual degree of importance in summer. If winter is compared with summer, opening hours of winter and summer are the same, that is, from 8:00 to 22:00, but summer is higher in a degree of importance, longer in a time zone, and steeper in rising, and larger in a peak size than winter.
As described above, when a degree of importance is simply set based on opening hours or the like depending on a hunch, the set degree of importance does not match the actual degree of importance in the peak size or the change inclination. Further, the number of visitors used to calculate the degree of importance is influenced by a season such as a daylight-saving time or daylight hours, and also influenced by a surrounding environment such as attending and leaving time of schools or attending and leaving time of companies. Thus, when a temporal change in a degree of importance is fixedly set in advance, it is difficult to cope with a change of a season or a surrounding environment.
Furthermore, when a degree of importance is determined from a moving image to adjust an image quality, if there is a determination error, there is a case in which it is difficult to set a high image quality when a moving image needs to be displayed at a high image quality. For example, when a face detection result is used as a degree of importance, if a person passes in front of a monitoring camera while looking away from it, there is a problem in that it is difficult to detect a face, and it is difficult to switch to a high image quality.
The present technology was made in light of the above problems, and it is desirable to provide an image encoding device, an image encoding method, and an image encoding program which are capable of encoding a moving image using a parameter according to a change in an actual degree of importance, an imaging device that sets a degree of importance according to a change in an actual degree of importance and photographs a moving image, an image encoding device that sets a degree of importance according to a change in an actual degree of importance, a photographing system having the same, a photographing recording system, an image encoding method, and an image encoding program.
An image encoding device according to the present technology includes an image quality control parameter calculating unit that calculates an image quality control parameter based on a degree of importance of a past time corresponding to a current time in a degree of importance period which is a period of a degree of importance of a plurality of input images which are consecutively input, and an image encoding unit that encodes the input images using the image quality control parameter and generates video data.
A photographing system according to the present technology includes the image encoding device, an imaging unit that photographs a subject and generates a video signal, and a signal processing unit that processes the video signal and generates the input image.
A photographing recording system according to the present technology includes the photographing system, and a recording device that is connected to perform communication with the photographing system, and records video data generated by the image encoding device.
An image encoding method according to the present technology includes calculating an image quality control parameter based on a degree of importance of a past time corresponding to a current time in a degree of importance period which is a period of a degree of importance of a plurality of input images which are consecutively input, and encoding the input images using the image quality control parameter and generating video data.
An image encoding program according to the present technology causes a computer to function as an image quality control parameter calculating unit that calculates an image quality control parameter based on a degree of importance of a past time corresponding to a current time in a degree of importance period which is a period of a degree of importance of a plurality of input images which are consecutively input, and an image encoding unit that encodes the input images using the image quality control parameter and generates video data.
According to the present technology, an image quality control parameter is decided using a degree of importance of a corresponding time in a previous degree of importance period, and thus it is possible to encode an input image using a parameter according to a change in an actual degree of importance and generate video data.
As will be described below, there are other embodiments in the present technology. Thus, the disclosure is intended to provide a part of the present technology and not intended to limit the scope of the technology described and claimed herein.